Multi-Well Pad Control: RTU vs. PLC

Multi-Well Pad Control: RTU vs. PLC

The world’s annual energy consumption of oil and gas will steadily increase from less than 200 quadrillion BTU in 2015 to nearly 250 quadrillion BTU by 2040, according to projections from the U.S. Energy Information Administration.

With demand continuing to grow, oil and gas producers will need to find new and better ways to capture energy resources. And they must do so while managing financial factors, such as dynamic pricing and production costs.

The most successful upstream producers will be those that embrace new technologies. 

There is already a shift occurring in the upstream oil and gas industry. Operators are moving from simplistic, vertically drilled, single-well pad fields to laterally drilled, multi-well pads.

These multi-well pads typically consist of anywhere from four to 12 wells – although some operators are reaching as many as 52 wells on just one pad.

These advancements have increased efficiency in upstream production, particularly in unconventional areas. But they also place much greater demands on well pad control systems.

As a result, operators and equipment suppliers must reconsider their control-system approach for multi-well pad operations.

Control Limitations

For decades, the remote terminal unit (RTU) was the best control technology that could be implemented in upstream oil and gas production.

It was rugged, power conservative and could handle the lower-bandwidth communication networks between the SCADA and the production site.

Increasingly, however, oil and gas producers have demanded more from their RTUs. And we’ve reached a point today where the modern multi-well pad has pushed the limits of RTU technology to its capacity.

Producers are now seeking a better solution to help them be more efficient and reduce costs, such as a programmable logic controller (PLC).

These controllers are modular, scalable and capable of handling a wide variety of communications and application support.

PLCs have not traditionally been built for inhospitable and harsh environments. But today’s modern well pads have environmentally controlled buildings, and utility or generator power. This creates an ideal environment for PLCs.

A Modular and Scalable Option

A modular and scalable PLC control architecture can address the challenges experienced with RTUs.

A modular system design means that PLCs can be configured in many ways. This enables oil and gas operators to monitor and control a wide variety of field instruments.

A modular PLC also supports communications for many different network types.

From a scalability standpoint, PLCs offer libraries of pre-developed and documented code that can be quickly added and configured onsite. This minimizes the need for a technician with specialized expertise to write new code when hardware is added.

Instead, operators need only enable and configure the required data from the HMI to commission the equipment.

Remote I/O functionality is another key component of a PLC’s scalability. PLCs that offer native remote I/O functionality can save on installation costs compared to RTUs. Programming in the PLC environment allows program changes and the addition of I/O without needing to shut down the process.

Such online editing capabilities are not available in traditional RTUs, as they must be taken offline to accept the changes. Due to lost production, such downtime is unacceptable in a modern, multi-well pad environment.

An Attractive Alternative

Multi-well pads have made data and application requirements in upstream operations greater than ever.

RTUs remain a feasible option, but their memory limitations, added maintenance requirements and overall higher production costs provide a strong incentive for operators to consider a better alternative.

Modular and scalable PLCs are capable of handling the scalable architectures required by modern well pads. They also are more efficient, and can help reduce installation, operating and maintenance costs.

For more information on Rockwell Automation oil and gas technologies, services and solutions, please see our onshore exploration and production solutions

Zack Munk
Posted July 31, 2017 By Zack Munk, Onshore Upstream Oil & Gas Business Development Manager, Rockwell Automation
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